Selection of decoding level at signal forwarding devices

ABSTRACT

In response to an instruction received from a base station, a signal forwarding device applies a signal forwarding scheme selected from a plurality of signaling forwarding schemes by a scheduler. The signal forwarding scheme may be applied by the signal forwarding device to forward signals from the base station to a user equipment (UE) device and/or from the UE device to the base station. The scheduler selects the signal forwarding scheme based on channel characteristics of the channel between the signal forwarding device and the UE device and/or the channel between the signal forwarding device and the base station. Although at least some of the channel characteristics are determined by the base station, at least some of the channel characteristics can be determined by the signal forwarding device in some situations.

CLAIM OF PRIORITY

The present application is a continuation of U.S. application Ser. No.15/772,211, filed Apr. 30, 2018 and entitled “SELECTION OF DECODINGLEVEL AT SIGNAL FORWARDING DEVICES”; which is a national stageapplication of PCT/US2016/059522, filed Oct. 28, 2016 and entitled“SELECTION OF DECODING LEVEL AT SIGNAL FORWARDING DEVICES”; which claimspriority to Provisional Application No. 62/248,459, entitled “RELAYSCHEME SELECTION BASED ON PILOT SIGNALS TRANSMITTED BY THE RELAY AND THEUSER EQUIPMENT,” filed Oct. 30, 2015, all assigned to the assigneehereof and hereby expressly incorporated by reference in their entirety.

FIELD

This invention generally relates to wireless communications and moreparticularly to selecting a level of decoding at signal forwardingdevices.

BACKGROUND

Some communication systems utilize a signal forwarding device, such as arepeater station, relay station or a self-backhauled station tofacilitate the transfer of information between user equipment (UE)devices and a core network. The signal forwarding device is typicallynot connected directly to the core network but still provides service tothe UE devices by forwarding information to and from the UE devices anda base station which is connected to the core network. Where the signalforwarding device is a repeater, the repeater simply retransmitsdownlink signals received from another base station to the UE device andretransmits uplink signals received from the UE device to the other basestation. Although the repeater may apply limited signal processing tothe incoming signal such as filtering, frequency shifting, andamplification, a repeater will not decode the incoming signal that is tobe forwarded. Relay stations and self-backhaul stations perform at leastsome signal processing before retransmitting the information. Suchprocessing can vary from partial decoding to complete decoding of theincoming signal. For example, the incoming signal can be completelydecoded and used to generate a new signal or the incoming signal may notbe completely decoded but still used to transmit the forwarded outgoingsignal. Some of the various levels of processing (forwarding techniques)are sometimes referred to as amplify and forward (AF), partial decodingand forward (PDF) and decode and forward (DF) schemes.

SUMMARY

In response to an instruction received from a base station, a signalforwarding device applies a signal forwarding scheme selected from aplurality of signaling forwarding schemes by a scheduler. The signalforwarding scheme may be applied by the signal forwarding device toforward signals from the base station to a user equipment (UE) deviceand/or from the UE device to the base station. The scheduler selects thesignal forwarding scheme based on channel characteristics of the channelbetween the signal forwarding device and the UE device and/or thechannel between the signal forwarding device and the base station. Inaccordance with one exemplary technique, the channel characteristics aredetermined at least from a reference signal received and retransmittedby the signal forwarding device and a reference signal transmitted bythe signal forwarding device. In accordance with another exemplarytechnique, at least some of the channel conditions are determined by thesignal forwarding device and conveyed to the scheduler through the basestation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communication system including asignal forwarding device and a base station.

FIG. 2 is a block diagram of a wireless communication system for anexample where the channel information transmitted by the signalforwarding device includes channel characteristics.

FIG. 3 is a block diagram of the wireless communication system for anexample where the base station determines the channel information.

FIG. 4 is block diagram of an example of a channel evaluator suitablefor use in the exemplary system described with reference to FIG. 3 .

FIG. 5 is a block diagram of an example of where the retransmitted UEreference signal and the SFD reference signal are transmitted with codedivision multiplexing (CDM).

FIG. 6 is a flow chart of an example of a method of managing signalforwarding schemes at a signal forwarding device.

FIG. 7 is a flow chart of an example of a method of managing signalforwarding schemes at a signal forwarding device where the channelinformation includes channel characteristics determined by the signalforwarding device.

FIG. 8 is a flow chart of an example of a method of managing signalforwarding schemes at a signal forwarding device where the channelinformation includes a retransmitted UE reference signal.

FIG. 9 is a flow chart of an example of a method at a base station ofmanaging signal forwarding schemes.

FIG. 10 is a flow chart of an example for performing steps 908 through912 of FIG. 9 .

DETAILED DESCRIPTION

As discussed above, communication systems often employ repeaters, relaysand self-anchored base stations to forward signals transmitted betweenbase stations and the UE devices served by the base stations. Signalsmay be forwarded from the base station to the UE device, from the UEdevice to the base station or both. In conventional systems, the signalforwarding device (repeater, relay, etc.) typically only performs onetype of signal forwarding scheme. For example, the signal forwardingdevice may be a repeater where signals are retransmitted with nodecoding of the incoming signal. In other situations, the signalforwarding device may be a relay where the incoming signal is at leastpartially decoded and used to generate the forwarded signal. In theexamples discussed herein, however, the signal forwarding device is ableto apply any one of a plurality of signal forwarding schemes where theapplied scheme is selected by a scheduler. The scheduler may be part of,or connected to, the base station where the base station sends aninstruction that indicates the selected signal forwarding scheme to thesignal forwarding device. The channel characteristics may be determinedby the base station, the signal forwarding device, or both.

The channel characteristics between the UE device and the signalforwarding device are continually changing due to the mobility of the UEdevice and/or changes in the interference level due to traffic-load. Inother scenarios, the signal forwarding device might be mobile and thechannel characteristics between the signal forwarding device and thebase station are also changing. Since, all these conditions could impactthe channel capacity of each link it is beneficial if the signalforwarding schemes are adaptive to such changes. For example, when theUE device is very close to the signal forwarding device, the receivedSNR of the UE device signal at the signal forwarding device receiverallows the signal forwarding device to decode the signal with a low biterror rate (BER).

FIG. 1 is a block diagram of a wireless communication system 100including a signal forwarding device 102 and a base station 104. Thebase station 104 provides wireless communication service to one or moreuser equipment (UE) devices 106 where the base station 104 exchangeswireless signals directly with the UE device 106 or through the signalforwarding device 102. For the examples herein, a scheduler 108 assignscommunication resources for serving the UE device 106 as well asperforming the functions for selecting the signal forwarding scheme tobe used by the signal forwarding device 102. The base station 104 isconnected to a core network 110 through a backhaul 112 in accordancewith known techniques. The scheduler 108 may be part of the base station104 or may be connected to the base station 104, either directly orthrough the core network 110. Although other techniques may be used, thebackhaul 112 is typically a wired backhaul that may include cabling,wires, fiber optic cables, and electronic equipment. Some other suitablebackhaul techniques include wireless links such as microwavepoint-to-point links, optical laser links, and other wirelessconnections that may use standard or proprietary protocols.

The signal forwarding device 102 is any fixed, mobile, or portableequipment that preforms the functions described herein. For example, thesignal forwarding device 102 may be a fixed device or apparatus that isinstalled at a particular location at the time of system deployment.Examples of such equipment include fixed base stations or fixedtransceiver stations. In some situations, the signal forwarding device102 may be mobile equipment that is temporarily installed at aparticular location. Some examples of such equipment include mobiletransceiver stations that may include power generating equipment such aselectric generators, solar panels, and/or batteries. Larger and heavierversions of such equipment may be transported by trailer. In still othersituations, the signal forwarding device 102 may be a portable devicethat is not fixed to any particular location. Accordingly, the signalforwarding device 102 may be a portable user device such as UE device insome circumstances. In some implementations, the signal forwardingdevice 102 may be a base station, eNB, or access point that performssignal forwarding functions in addition to serving UE devices. Forexample, a self-backhauled eNB may be configured to perform signalforwarding functions for some UE devices in addition to directly servingother UE devices utilizing the wireless backhaul to the base station104.

The base station 104 provides wireless communication service to one ormore UE devices 106 by receiving uplink signals and transmittingdownlink signals to the UE devices. For the example of FIG. 1 , thesignal forwarding device 102 forwards the downlink signals 114 to the UEdevice 106 and forwards the uplink signals 116 to the base station 104.Therefore, the UE device 106 transmits an incoming UE uplink signal 116that is received and forwarded by the signal forwarding device 102 as aforwarded uplink signal 118. The signal forwarding device 102 receivesincoming downlink signals 114 transmitted by the base station 104 andforwards a forwarded downlink signal 120 to the UE device 106 that isbased on the incoming downlink signal 114. The forwarded uplink signal118 and the incoming downlink signal 114 are transmitted within abase-station-to-signal forwarding-device channel (BS-SFD channel) 122.For the examples herein, the BS-SFD channel 122 is within a singlefrequency band although different sub-bands may be used for uplink anddownlink directions. The forwarded downlink signal 120 and the incominguplink signal 116 are transmitted within a UE-to-signalforwarding-device channel (UE-SFD channel) 124. For the examples herein,the UE-SFD channel 124 is within a single frequency band althoughdifferent sub-bands may be used for uplink and downlink directions. Anycombination of frequency bands and frequency sub-bands may be used forthe channels. In addition to the channels that link through the signalforwarding device 102 and under the appropriate conditions, the basestation 104 can communicate with the UE device 106 directly through adirect channel 126 for uplink transmissions, downlink transmissions, orboth. As a result, the signal forwarding device 102 may only forwardsignals in either the uplink or downlink direction in some situations.

The signal forwarding device 102 is capable of applying any one of aplurality of signal forwarding schemes when forwarding a signal. Asdiscussed herein, a signal forwarding scheme is based on the parameters,techniques, and/or level of processing applied to the incoming signal togenerate the forwarded signal. The number and types of signal forwardingschemes that a signal forwarding device 102 is capable of applyingdepends on the particular implementation. For the examples herein, thesignal forwarding schemes are categorized into three basic groups whereeach group includes at least one scheme. Repeater signal forwardingschemes generally include retransmission schemes where the incomingsignal is received and retransmitted. At a minimum, the incoming signalis amplified and retransmitted as the forwarded signal. In some repeaterschemes, some processing is applied to the incoming signal. For example,the incoming signal may also be filtered and/or frequency shifted.Generally, however, the incoming signal is not demodulated or decoded ina repeater signal forwarding scheme. Repeater schemes are sometimesreferred to as amplify and forward (AF) schemes. Relay signal forwardingschemes include at least some decoding of the incoming signal to createthe forwarded signal where the level of decoding can range from minimalto complete decoding of the incoming signal. Complete decoding includesfully decoding the incoming signal to extract the payload and thenapplying the decoded data to generate the new forwarded signal. Completedecoding schemes are sometimes referred to as decode and forward (DF)schemes. Several proposed techniques include partial decoding of theincoming signal to transmit a forwarded signal without complete decodingto extract the data from the signal. For partial decoding, the incomingsignal may be demodulated to obtain the raw demodulated symbols whichare modulated and retransmitted. These schemes are sometimes referred toas partial decode and forward (PDF) schemes. Accordingly, the signalforwarding device 102 may be capable of applying any number of signalforwarding schemes categorized as AF, PDF and DF schemes. In somesituations, the signal forwarding device 102 is capable of applying atleast one scheme of each category. In other situations, the signalforwarding device 102 may only apply schemes from a single group. Forexample, the signal forwarding device may only be capable of applyingseveral different PDF schemes. For a particular example discussedherein, however, the signal forwarding device 102 is capable of applyingat least one AF scheme, one PDF scheme and one DF scheme. In addition,different signal forwarding schemes can be applied to uplink anddownlink directions for a particular UE device 106.

For the example of FIG. 1 , the signal forwarding device 102 includes atransmitter 128, receiver 130, a signal forwarding processor 131,retransmission processor 132, relay processor 134, controller 136 andantenna 138 as well as other electronics, hardware, and code. Thevarious functions and operations of the blocks described with referenceto the signal forwarding device 102 may be implemented in any number ofdevices, circuits, or elements. Two or more of the functional blocks maybe integrated in a single device, and the functions described asperformed in any single device may be implemented over several devices.For example, the controller 138 may perform functions of the signalforwarding processor 131, retransmission processor 132 or relayprocessor 134 in some circumstances. The controller 136 includes anycombination of hardware, software, and/or firmware for executing thefunctions described herein as well as facilitating the overallfunctionality of the signal forwarding device 102. An example of asuitable controller 136 includes code running on a microprocessor orprocessor arrangement.

The transmitter 128 includes electronics configured to transmit wirelesssignals to UE devices 108 as well as to the base station 104. In somesituations, the transmitter 128 may include multiple transmitters. Thereceiver 130 includes electronics configured to receive wireless signalsfrom UE devices as well as from the base station 104. In somesituations, the receiver 130 may include multiple receivers. Thereceiver 130 and transmitter 128 receive and transmit signals,respectively, through an antenna 138. The antenna 138 may includeseparate transmit and receive antennas. In some circumstances, theantenna 138 may include multiple transmit and receive antennas. Thetransmitter 128 and receiver 130 in the example perform radio frequency(RF) processing. The receiver 130 in the example, therefore, may includecomponents such as low noise amplifiers (LNAs), and filters. Thetransmitter 130 may include filters and amplifiers. In some situations,the transmitter and/or receiver may also include a signal mixer. Othercomponents may include isolators, matching circuits, and other RFcomponents.

The signal forwarding processor 131 includes electronics for performingsignal forwarding functions to generate the forwarded signal. The signalforwarding processor 131 is capable of applying at least two differentsignal forwarding schemes to the received signal. In someimplementations, the signal forwarding processor 131 is capable ofapplying any one of a number signal forwarding schemes where each schemeincludes a different level of decoding of the incoming signal. For theexample discussed with reference FIG. 1 , the signal forwardingprocessor 131 includes the retransmission processor 132 and the relayprocessor 134. In some situations, the signal forwarding processor 131may include only the relay processor 134. In such situations, the relayprocessor 134 is capable of applying at least two signal forwardingschemes including different levels of decoding which may includedecoding for PDF and/or DF signal forwarding schemes. For example, therelay processor 134 may be capable of applying a PDF scheme and DFscheme.

The retransmission processor 132 includes electronics for performingsignal forwarding functions that do not include decoding of the incomingsignal. The retransmission processor 132, therefore, performs repeatertype tasks where such tasks may include, for example, filtering andamplification. In some cases, the tasks may also include frequencyshifting to shift the incoming signal from one frequency fortransmission at another frequency. In response to, or in conjunctionwith, the controller 136, the retransmission processor 132 receives anincoming signal from the receiver and processes the signal forretransmission through the transmitter 128. The retransmitted signal isa forwarded downlink signal 120 where the incoming signal is an incomingdownlink signal 114 transmitted from the base station 104. Theretransmitted signal is an uplink forwarded signal 118 where theincoming signal is an incoming uplink signal transmitted by a UE device108. The retransmission processor may have components that can beconsidered to be part of the receiver 130 and or transmitter 128. Forexample, at least some amplification of the retransmitted signal as partof the retransmission processor 132 processing may be performed by thetransmitter 128. In some ways, the retransmission processor can beconsidered to be applying a signal forwarding scheme that has a level ofdecoding equal to zero

The relay processor 134 includes a decoder 140 and an encoder 142 and isany circuit, combination of circuits, or device that can process theincoming signal to generate the forwarded signal beyond merelyretransmitting the incoming signal. For the examples herein, the relayprocessor 134 is capable of performing a complete decode and forward(DF) scheme and at least one partial decode and forward (PDF) scheme. Insome situations, however, the relay processor 134 may be capable ofperforming numerous PDF schemes. In response to, or in cooperation with,the controller 136, the relay processor 134 processes the incomingsignal to generate a forwarded signal in accordance with the selectedrelay scheme. As a result, the controller selects the appropriate PDFscheme or DF scheme to manage the relay processing function.

For the examples herein, the controller 136 selects the signalforwarding scheme based on a signal forwarding scheme selectioninstruction 144 provided by the base station serving the UE device forwhich signals are forwarded. Based at least partly on channelinformation 146, the scheduler 108 selects the signal forwarding schemethat should be used by the signal forwarding device 102. In one example,the signal forwarding device 102 provides the base station 104 with atleast some of the channel information 148. The channel information 142,however, may include any combination of channel measurements made by thesignal forwarding device 102, channel measurements made by the basestation 104, channel quality indicators provided by the signalforwarding device 102, and/or channel estimation.

In some situations, the channel information 148 provided by the signalforwarding device 102 is a forwarded reference signal received from theUE device 106. In still other situations, the channel information 148 isa threshold indicator indicating whether the quality of channel is abovea threshold. In one example, the base station 102 uses channelestimation and evaluation techniques to evaluate a reference signalsreceived and retransmitted by the signal forwarding device 102.

FIG. 2 is a block diagram of communication system 100 for an examplewhere the channel information 148 transmitted by the signal forwardingdevice 102 includes channel characteristics 202. In one example, thechannel characteristics 202 include parameters or other indicators thatare indicative of channel measurements taken by the signal forwardingdevice 102. In another example, channel characteristics 202 include oneor more indicators indicating whether a measurement or another parameteris above or below a threshold. In some situations, the indicator mayindicate whether the quality of a particular channel is above athreshold.

For the examples of FIG. 2 , the signal forwarding device 102 receives areference signal 204 from the UE device 106. A pilot signal is anexample of a suitable reference signal 204. The signal forwarding device102 processes the reference signal 204 to measure one or more channelcharacteristics of the channel (UE-SFD) 124 between the signalforwarding device 102 and the particular UE device 106. For theexamples, the controller 136 is configured to process the referencesignal 204 in cooperation with the receiver 130 to determine the channelmeasurements. Examples of suitable measurements include signal to noiseratio (SNR), received signal strength, signal-to-interference-plus-noiseratio (SINR) where SINR is typically preferred.

As mentioned above, the resulting channel measurements can be sent tothe base station 102 as the channel characteristics 202. In somesituations, the channel measurements are processed further by thecontroller 136 to generate other parameters based on the measurements.As described above, such a parameter may be an indicator indicatingwhether the quality of the channel is above a threshold.

The channel characteristics 202 can be sent using a data channel orcontrol channel. In one example, the channel characteristics 202 is sentto the base station from the signal forwarding device 102 in a wirelesschannel. In some situations, the BS-SFD CH channel is used to transmitthe instructions. In other situations, the instruction is transmittedover a separate wireless channel such as a point-to-point microwavelink. Accordingly, any suitable channel may be used to transmit theinstructions.

In some situations, the signal forwarding device 102 forwards ascheduling request received from the UE device to the base station in adata channel. In these situations, the associated control channelcontains an indicator field indicating the channel condition of theUE-SFD channel. In other situations, the signal forwarding device 102sends a message to the bases station 104 requesting a resource for theUE device transmission. This request includes the channel conditions.

A receiver 206 in the base station 104 receives the channelcharacteristics information 202 and forwards the information to thescheduler 108. The scheduler 108 evaluates the channel characteristics202, and possibly other channel information, to select signal forwardingscheme to be used by the signal forwarding device 102. Other channelinformation 146 available to the scheduler 108 may include the channelquality of channel characteristics of the direct channel (UE-BS channel)126 between the UE device 106 and the base station 104. The selectionmay be based on several parameters or information in addition to thechannel information 148. Some examples of data that may be evaluated bythe scheduler 108 to select the scheme include processing latency at thesignal forwarding device, the required quality of service (QoS) for thelink to the UE device, available capacity at the base station 102, andavailable coding rates supported by the base station. Each of thefactors may be weighted with different importance in selecting thesignal forwarding scheme. For example, in some situations, theprocessing latency at the signal forwarding device may be the highestpriority in selecting the signal forwarding scheme. Where the signalforwarding scheme requires decoding of the incoming signal, severaldecoding iterations (Turbo decoder) to decode the signal which mayrequire tens or hundreds of microseconds. Accordingly, the selection ofthe signal forwarding scheme typically involves a trade-off between highreliability and the latency of the retransmission of the signal. Highreliability is achieved where the signal forwarding scheme decodes thesignal completely and then transmits at the cost of higher latency. Thescheduler 108 may select the same signal forwarding scheme for theuplink signal forwarding and the downlink signal forwarding or mayselect different schemes for each direction. In some situations, thescheduler 108 may select a signal forwarding scheme for the signalforwarding device 102 to use in one direction and may schedule resourcesfor direct communication through the UE-BS CH 126 for the otherdirection.

A transmitter 208 in the base station 104 forwards the informationregarding the selected signal forwarding scheme to the signal forwardingdevice 102 in the signal forwarding scheme instruction 144. Theinstruction 144 may be sent using any adequate communication channel. Inone example, the signal forwarding scheme instruction is sent from thebase station to the signal forwarding device 102 in a wireless channel.In some situations, the BS-SFD CH channel is used to transmit theinstructions. In other situations, the instruction is transmitted over aseparate wireless channel such as point to point microwave link.Accordingly, any suitable channel may be used to transmit theinstructions. For example, the instruction 144 may be transmitted in aPhysical Downlink Control Channel (PDDCH) message.

The signal forwarding device 102 receives the instruction 144 and, inresponse to the instruction 144, applies the selected signal forwardingscheme to the incoming signal(s). In response to the instruction, thecontroller 136 applies the selected signal forwarding scheme to theincoming signal by invoking the signal forwarding processor 131. Wherethe relay processor 134 is used for the signal forward processing, thecontroller 136 manages the relay processor 134 to apply the appropriatesignal forwarding scheme and level of decoding/processing to theincoming signal (whether the incoming UL signal 116 or the incoming DLsignal 114). For example, where the instruction indicates that the PDFscheme should be applied, the controller 136 manages or otherwisecontrols the relay processor 134 to apply the selected PFD scheme to theincoming signal and to generate the forwarded signal. As mentionedabove, different signal forwarding schemes may be applied in thedifferent directions.

FIG. 3 is a block diagram of the communication system 100 for an examplewhere the base station 104 determines the channel information 146. Thebase station includes a channel evaluator 302 that can obtain channelinformation for at least one of the channels involving the signalforwarding device 102. For the example of FIG. 3 , the channel evaluator302 is capable of determining channel characteristics for the BS-SFDchannel 122, the UE-BS channel 126 and the UE-SFD channel 124. The UEdevice 106 transmits a UE reference signal 204 such as a pilot signalthat is received by the signaling forwarding device 102. The signalingforwarding device 102 retransmits the received UE reference signal as aretransmitted UE reference signal 304. The signal forwarding device alsotransmits is own reference signal 306. As discussed below, the techniquefor transmitting the retransmitted UE reference signal 304 and the SFDreference signal 306 typically depends on the type of communicationchannel. For example, in a system employing time division multiplexing(TDM) channels, the two reference signals 304, 306 can be transmitted atdifferent times. In systems employing code division multiplexing (CDM)channels, the two channels 304, 306 can be coded and combined beforetransmission.

The base station 104 receives the retransmitted UE reference signal 304and the SFD reference signal 306. The channel estimator 302 processesthe signals and determines the channel characteristics for the UE-SFDchannel 124 and the BS-SFD channel 122. For the example, the channelevaluator 302 also determines the channel characteristics of the directUE-BS channel 126. Channel information 146 based on the channelcharacteristics are forwarded to the scheduler 108. Based on the channelinformation 146 and other factors, the scheduler 108 determines whetherthe signal forwarding device 102 should be used to forward signals and,if so, selects the signal forwarding scheme that should be used by thesignal forwarding device 102. The scheduler 108 schedules communicationresources and sends, through the base station 104, the schedulinginformation to the UE devices as well as sending the signal forwardingscheme instruction 144 to the signal forwarding device 102.

FIG. 4 is block diagram of an example of a channel evaluator 302suitable for use in the exemplary system described with reference toFIG. 3 . The channel evaluator 302 includes a channel estimationfunction that can be represented by channel estimators 402, 404, 406 anda gain computation function that can be represented by gain computers408, 410, 412. One channel estimator 402 receives the SFD referencesignal 306 through the BS-SFD channel 118 and provides channelcoefficients based on measurements of the received SFD reference signal306. The gain computer 408 evaluates the channel coefficients providedby the channel estimator 402 to compute the gain. The computed gain maybe signal-to-noise ratio (SNR) or the signal-to-noise-plus-interferenceratio (SNIR). Another channel estimator 406 receives the UE referencesignal 204 through the UE-BS channel 126 and provides channelcoefficients based on measurements of the received UE reference signal204. The gain computer 412 evaluates the channel coefficients providedby the channel estimator 406 to compute the gain. The channel estimator404 receives the retransmitted UE reference signal 304 through theBS-SFD channel 118. In situations where the channel evaluator is onlydetermining whether to use the signal forwarding device 102, the gaincomputer 410 evaluates the channel estimates to compute the gain for theretransmitted UE reference signal. The gains computed by the gaincomputers 408, 410, 412 can be compared to determine whethercommunication should be directly with the UE device, through the signalforwarding device 102, or both. For situations where the signalforwarding scheme of the signal forwarding device 102 is selected,however, additional information regarding the UE-SFD channel 124 is usedto make the determination. For the example of FIG. 4 , a channelseparation processor 414 uses the channel estimate of the BS-SFD channel118 to determine characteristics of the UE-SFD channel 124. The channelseparator may apply any single signal processing algorithm orcombination of signal processing algorithms to separate the twochannels. An example of a suitable technique includes using blind sourceseparation (BSS) techniques. The channel separation processor 414determines the channel characteristics of the UE-SFD channel. Thechannel coefficients of the UE-SF channel, for example can bedetermined. The gain computer 410 determines the gain for the UE-SFDchannel 124. Based on the gains of the channels, the channel/schemeselector 416 determines whether the signal forwarding device should beused and, if so, what signal forwarding scheme should be used. Theparticular decision technique used by the channel/scheme selector 416may be based on any of a variety of algorithms or decision criteria. Thefollowing decision technique and criteria provides one example.

For the example, the SNR of each channel is used to determine whetherthe signal forwarding device should be used and, if so, the SNR of eachchannel is compared to thresholds to select the signal forwarding schemeto be used by the signal forwarding device 102. If the SNRUE-SFD ofUE-SFD channel 124 plus the SNRBS-SFD of BS-SFD channel 122 is greaterthan the SNRUE-BS of UE-BS channel 126, it is determined that the signalforwarding device 102 should be used. In some situations, the compositechannel quality of UE-to-SFD+SFD-to-BS SNR is sufficient to determine ifthe SFD-to-BS link is fixed due to fixed locations of the relay and thebase station. As a result, in some situations, the channel estimator402, channel separator 414, and gain computer 408 can be omitted indetermining whether the signal forwarding device should be used.

For the example, the signal forwarding device 102 is capable of applyingthree signal forwarding device schemes including an AF scheme, a DFscheme, and a PDF scheme. If the signal forwarding device is to be used,the criteria is applied to determine which scheme should be used. Thecriteria may include any number of factors and thresholds. Some examplesof factors that can be used to select the signal forwarding schemeinclude the decoder's processing delay (for example, number ofiterations for Turbo decoders) at the base station 104, the decoder'sprocessing delay at the signal forwarding device 102 the quality ofservice (QoS) requirements of the transmission, the latency requirementsof the transmission, and whether the signal forwarding device 102 isfixed or mobile. Specific thresholds may be determined using simulationstypically depend on the particular implementation of the differentsystem components. For example, the expected decoder delay at the signalforwarding device 102 may be considered when determining whether to usea PDF scheme. In one example, the DF scheme is used when the UE-SFDchannel 124 is high quality and when the expected decoding delay can betolerated to achieve the required latency for the transmission. In suchan example, the AF scheme is used when the UE-SFD channel 124 is ofsomewhat high quality and the PDF is used when the UE-SFD channel 124 isof mid quality where the delay for full decoding cannot be tolerated toachieve the required latency for the transmission.

There are several options, however, for selecting the signal forwardingscheme depending upon different scenarios. For example, in some casesthe UL transmission from the UE device is decoded at the signalforwarding device when the received signal SINR is strong enough for asuccessful early decoding (few decoding iterations). In this case, theDF scheme is appropriate. However, in another scenario, where thereceived signal SINR is not strong enough, it is preferred that thesignal forwarding device not make an attempt to decode the signalbecause it may take a maximum number of iterations to decode. In thiscase, it might be better for the forwarding device to apply a PDF schemeand allow the base station to decode the signal. In addition toconsidering the received SINR, the QoS (latency) requirements may needto be considered such that it may be determined that the signalforwarding device should not delay the transmission by not evenattempting to decode the transmission and should simply apply a PDFscheme.

Exemplary criteria with thresholds includes the following:

If threshold A<SNR_(UE-SFD), then use DF scheme;

If threshold B<SNR_(UE-SFD)<threshold A, then use AF scheme;

If threshold C<SNR_(UE-SFD)<threshold B, and decoder delay at signalforwarding device can be tolerated to achieve latency requirement oftransmission, then use DF scheme;

If thresholdC<SNR_(UE-SFD<threshold B, and decoder delay at signal forwarding device cannot be tolerated to achieve latency requirement of transmission, then use PDF scheme;)

If SNR_(UE-SFD)<threshold C, then use DF scheme, where thresholdA>threshold B>threshold C.

Therefore, for the above example, the DF scheme is used when the SNR ofthe UE-SFD channel is above a very high threshold, below a very lowthreshold, and at mid value where the decoding delay can be tolerated.The rationale for such a scheme selection technique may be based on thefollowing. Where the EE-SFD channel quality is very high, the decodingdelay at the signal forwarding device is very low and can be toleratedfor all transmission. For example, where a Turbo decoder is used, thenumber of decoding iterations is relatively low because the symbols areof high quality with few errors. The DF scheme may also be needed wherethe channel quality is sufficiently low that full decoding at the signalforwarding device is necessary to ensure a minimum error rate at thedestination (e.g., base station). Where the channel quality is stillrelatively high but less than the highest threshold, the AF scheme maybe sufficient to forward the signal and maintain the minimum error rateat the destination (e.g., base station).

At a midrange quality of the UE-SFD channel, the DF scheme can be usedwhere the resulting decoding delay can be tolerated. Otherwise, a PDFscheme may be used where the signal forwarding device demodulates andforwards the detected symbols without decoding the incoming signal. Thisresults in a compromise between quality of the forwarded signal and theresulting latency.

FIG. 5 is a block diagram of an example of where the retransmitted UEreference signal and the SFD reference signal are transmitted with codedivision multiplexing (CDM). As mentioned above, in system using CDM,the retransmitted UE reference signal and the SFD reference signal canbe coded (scrambled) and then transmitted at the same time. For theexample of FIG. 5 , the UE reference signal is received at the signalforwarding device and coded with a UE scrambling code (such as a Walshcode). The SFD reference signal is coded with a SFD scrambling code(such as another Walsh code) and then combined with the coded UEreference signal. The combined coded signal is transmitted over theBS-SFD channel 122 to the base station 104. At the base station 104, theUE scrambling code and the SFD scrambling code are applied to theincoming combined reference signal 502. The application of the SFDscrambling code allows recovery of the SFD reference signal. Afterapplying the UE scrambling code to the incoming combined referencesignal 502, timing derived from the recovered SFD reference signal isapplied to the resulting decoded signal. Channel estimation and gaincomputation is performed on the resulting signal.

FIG. 6 is a flow chart of an example of a method of managing signalforwarding schemes at a signal forwarding device 102. Although themethod may be performed by other types of devices and in differentsystems, for the example, the method is performed in the signalforwarding device 102 described above.

At step 602, a UE reference signal 204 is received from the UE device106. An example of a suitable UE reference signal 204 is a pilot signal.The reference signal 204 is received through the UE-SFD channel 124.

At step 604, channel information 148 is transmitted to the base station104. The channel information 148 may include channel characteristics 202determined by the signal forwarding device, retransmission of the UEreference signal (retransmitted UE reference signal 304), a SFDreference signal 306 and/or other information related to the UE-SFDchannel 124 and/or the BS-SFD channel 122. Two exemplary methods arediscussed below including a method where the channel information 148includes reference signals 304, 306 and a method where the channelinformation 148 includes measured channel characteristics 202.

At step 606, a signal forwarding scheme instruction 144 is received fromthe base station 104. The signal forwarding scheme instruction 144identifies the signal forwarding scheme that should be applied by thesignal forwarding device 102.

At step 608, the signal forwarding device applies the signal forwardingscheme identified by the instruction to the incoming signal. Asdiscussed above, the incoming signal may be the downlink incoming signal114 from the base station 104 or may be the uplink incoming signal 116from the UE device 106. The signal forwarding device 102 may forwardsignals in one or both directions.

FIG. 7 is a flow chart of an example of a method of managing signalforwarding schemes at a signal forwarding device 102 where the channelinformation 148 includes channel characteristics 202 determined by thesignal forwarding device 102.

At step 702, a UE reference signal 204 is received from the UE device106. An example of a suitable UE reference signal 204 is a pilot signal.The reference signal 106 is received through the UE-SFD channel 124.

At step 704, channel characteristics of the UE-SFD channel 124 betweenthe UE and the signal forwarding device 102 are determined. The signalforwarding device 102 receives the UE reference signal 204 and performschannel estimation to determine channel coefficients of the UE-SFDchannel 124 for one example.

At step 706, an SFD reference signal 306, such as a pilot signal, istransmitted to the base station 104 through the BS-SFD channel 122.

At step 708, the channel characteristics 202 of the UE-SFD channel 124are transmitted to the base station 104. In some situations, the channelcharacteristics 202 are transmitted as parameters or values. Forexample, the channel coefficients of the UE-SFD channel can be sent inmessage to the base station 104. In other situations, the channelcharacteristics 202 are sent as an indicator of the whether a particularthreshold has been exceeded. For example, the channel characteristics202 may include an indicator indicating whether the quality of theUE-SFD channel is above a threshold.

At step 710, a signal forwarding scheme instruction 144 is received fromthe base station 104. The signal forwarding scheme instruction 144identifies the signal forwarding scheme that should be applied by thesignal forwarding device 102.

At step 712, the signal forwarding device 102 applies the signalforwarding scheme identified by the instruction to the incoming signal.As discussed above, the incoming signal may be the downlink incomingsignal 114 from the base station 104 or may be the uplink incomingsignal 116 from the UE device 106. The signal forwarding device 102 mayforward signals in one or both directions.

FIG. 8 is a flow chart of an example of a method of managing signalforwarding schemes at a signal forwarding device 102 where the channelinformation 148 includes a retransmitted UE reference signal 304.

At step 802, a UE reference signal 204 is received from the UE device106. An example of a suitable UE reference signal 204 is a pilot signal.The reference signal 106 is received through the UE-SFD channel 124.

At step 804, the UE reference signal 204 is retransmitted as aretransmitted UE reference signal 304. For the example, the UE referencesignal 204 is received, amplified and retransmitted with minimal or noprocessing.

At step 806, an SFD reference signal 306, such as a pilot signal, istransmitted to the base station 104 through the BS-SFD channel 122.

At step 808, a signal forwarding scheme instruction 144 is received fromthe base station 104. The signal forwarding scheme instruction 144identifies the signal forwarding scheme that should be applied by thesignal forwarding device 102.

At step 810, the signal forwarding device 102 applies the signalforwarding scheme identified by the instruction to the incoming signal.As discussed above, the incoming signal may be the downlink incomingsignal 114 from the base station 104 or may be the uplink incomingsignal 116 from the UE device 106. The signal forwarding device 102 mayforward signals in one or both directions.

FIG. 9 is a flow chart of an example of a method at a base station ofmanaging signal forwarding schemes.

At step 902, a UE reference signal 204 is received from the UE device106 through the UE-BS channel 126.

At step 904, UE-BS channel 126 is evaluated. In one example, channelestimation is performed on the channel to determine channel coefficientsand the gain of the channel. For example, the SNR or SNIR of the UE-BDchannel 126 can be computed.

At step 906, channel information 148 is received from the signalforwarding device 102. The channel information 148 may include channelcharacteristics 202 determined by the signal forwarding device,retransmission of the UE reference signal (retransmitted UE referencesignal 304), a SFD reference signal 306 and/or other information relatedto the UE-SFD channel 124 and/or the BS-SFD channel 122.

At step 908, it is determined whether the signal forwarding device 102should be used for communication with the UE device 106. The basestation 104 evaluates the channel information 148 and the channelevaluation of the UE-BS channel 126 and determines whether it ispreferred to communicate directly with the UE device 106 or tocommunicate through the signal forwarding device 102. In one example,the base station uses the channel information to evaluate the UE-SFDchannel 124 and the BS-SFD channel 144 and then compares the evaluationsof the three channels 122, 124, 126 to determine whether the signalforwarding device should be used. If it is determined that the signalforwarding device should not be used, the method continues at step 910where the base station communicates directly with the UE device 106through the UE-BS channel 126. Otherwise, the method continues at step912.

At step 912, the signal forwarding scheme to be used by the signalforwarding device 102 is selected. The scheduler 108 in cooperation withthe base station 104 selects the signal forwarding scheme based at leaston the channel information 144. In one example, channel evaluations ofthe three channels 122, 124, 126 are compared to select the signalforwarding scheme. In some situations, other information in addition tothe channel information is used to select the signal forwarding scheme.

At step 914, a signal forwarding scheme instruction 144 is transmittedto the signal forwarding device. The signal forwarding schemeinstruction indicates the selected signal forwarding device scheme.

At step 916, the base station communicates with the UE device 106through the signal forwarding device 102. The signal forwarding device102 applies the signal forwarding scheme identified by the instructionto the incoming signal. As discussed above, the incoming signal may bethe downlink incoming signal 114 from the base station 104 or may be theuplink incoming signal 116 from the UE device 106. The signal forwardingdevice 102 may forward signals in one or both directions.

FIG. 10 is a flow chart of an example for performing steps 908 through912 of FIG. 9 . The example of FIG. 10 is one of numerous techniquesthat can be used to select the signal forwarding scheme. The techniqueincludes comparing the SNR of the UE-SFD channel to three thresholdsincluding Threshold A, Threshold B and Threshold C, where Threshold A isgreater than Threshold B and Threshold B is greater than Threshold C.

At step 1002, it is determined whether the combined SNR of the UE-SFDchannel and the BS-SFD channel is greater than the SNR of the UE-BSchannel. If the combined SNR is not greater than the UE-BS channel SNR,the method continues at step 1004 where the bases station communicatesdirectly with the UE device 106 through the UE-BS channel and the signalforwarding device is not used. If the combined SNR is greater than theUE-BS channel SNR, the method continues at step 1006.

At step 1006, it is determined whether the SNR of the UE-SFD channel isgreater than Threshold A. If the SNR is greater than the threshold, themethod continues at step 1008 where the DF signal forwarding scheme isselected. Otherwise, the method continues at step 1010.

At step 1010, it is determined whether the SNR of the UE-SFD channel isless than Threshold C. If the SNR is less than the threshold, the methodcontinues at step 1008 where the DF signal forwarding scheme isselected. Otherwise, the method continues at step 1012.

At step 1012, it is determined whether the SNR of the UE-SFD channel isless than Threshold A but greater than Threshold B. If the SNR is therange, the method continues at step 1014 where the AF signal forwardingscheme is selected. Otherwise, the method continues at step 1016.

For the example, step 1016 is reached when the SNR of the UE-SFD channelis greater than Threshold C and less than Threshold B. At step 1016, itis determined whether the required maximum latency of the transmissionis greater than a latency threshold. If the decoding delay resultingfrom a full decode and forward (DF) signal forwarding scheme is lessthan the delay that can be tolerated for the transmission, it isdetermined that the latency requirement is greater than the latencythreshold and the method continues at step 1008. Otherwise, the methodproceeds to step 1018 where the PDF signal forwarding scheme isselected. Therefore, where the decoding delay is less than the maximumtolerable delay for the transmission, the DF signal forwarding scheme isselected. Where the decoding delay is greater than the maximum tolerabledelay for the transmission, the PDF signal forwarding scheme isselected.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

1. A method comprising: transmitting first information from a relaydevice to a base station, the first information indicating a quality ofa channel between the relay device and a user equipment (UE) device; anddetermining, at the base station in response to the first information,whether to wirelessly communicate with the UE device through the relaydevice.
 2. The method according to claim 1, further comprising:receiving the first information at the relay device from the UE devicebefore transmitting the first information, wherein transmitting thefirst information comprises forwarding the first information.
 3. Themethod according to claim 1, wherein the determining is performed basedon the first information and a second information, the secondinformation indicating a quality of a channel between the base stationand the UE device.
 4. The method according to claim 1, wherein the firstinformation further indicates that the quality of the channel is below athreshold.
 5. A relay device comprising a transmitter configured totransmit first information to a base station, the first informationindicating a quality of a channel between the relay device and a userequipment (UE) device, wherein the first information is configured tocause the base station to determine whether to wirelessly communicatewith the UE device through the relay device.
 6. A base stationcomprising: a receiver configured to receive first information from arelay device, the first information indicating a quality of a channelbetween the relay device and a user equipment (UE) device; and acontroller configured to determine, in response to receiving the firstinformation, whether to wirelessly communicate with the UE devicethrough the relay device.